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Enter the field unit name.

Select the Protocol type for the Internal Master field unit. The Protocol selection determines the rules by which a host can access the data in this Virtual Master's RTDB, via attachment to a Slave Channel. Available Protocol types are:

• Read/Write Internal RTU, not to DBM. This allows a host to both read data from the RTDB and write data directly to the device configured in the Source Channel/RTU.
• Read/Only Internal RTU. This allows a host to read data from the RTDB, but writes are not allowed. Data in the RTDB can be changed by ISaGRAF or by Internal Master polls from other RTDB locations, but not by an external host connected via Slave Channel.
• R/W RTU or to DBM if no Remapped Poll Record. This allows a host to read data from the RTDB and write data directly to the device configured in the Source Channel/RTU if there are matching poll records; otherwise, write data is stored directly into this Internal Master's RTDB registers. 

Enter the number of communication retries after a failed poll attempt.

If a poll attempt fails, poll will be sent again up to the configured number of "Com Retries" before the field unit is declared failed. 

Enter the starting holding register to contain the communication status for this field unit.  Each Comm Status takes 5 registers, beginning at the register configured in this parameter. The Comm Status Holdreg for each field unit in a configuration must be defined such that the five registers do not overlap other registers being used.

If the register is defined in the 30,xxx address range, the status values will be stored in the local device's RTDB (i.e., the RTDB defined as a child to this Field unit).  If the register is in the 40,xxx range, the values will be stored in the Status/Control Field Unit RTDB. The Comm Status Holdreg is optional, and can be set to 0 to disable the storage of status registers. See the section Communication Status Registers, for a description of the five Comm Status Register contents. 

Select this option to determine whether to produce a Report by Exception (RBE) flag when data in this unit's RTDB changes.

In the RTDB, for every data point, there are potentially 4 RBE flags associated with every data point. When the data point changes, the RBE flags are set. These flags are used to determine when new data needs to be reported to the HCP. 

Click the Edit Table button to define the Modbus polls to be sent to this unit. Note that the Poll Table only defines how the Modbus protocol is defined to operate for each set of data defined in the polls. The Poll Table doesn't actually do any of the polling itself. If you want any of these polls to be sent to the Field Unit on a regular basis, it should be referenced in one or more Scan Table entries in the Master Channel. 

Src Chan – Enter the Channel number of the RTDB containing the source data. This is either a Master Channel or Internal Channel instance number that must be defined under the Master Channels placeholder. 

Src RTU – Enter the Field Unit number of the RTDB containing the source data. This is the Unit Address configured in the properties of the field unit, not the instance number of the field unit ACE object, if they are different. 

Src Data – Enter the source register number for the starting register in the Field Unit's RTDB to begin retrieving data. 

Src Type - Enter the data type of the data being requested. See below for a discussion of Src Type options in the Master Channel. 

Src Count – Enter the number of registers to retrieve. The maximum number allowed in any poll is the same as for Modbus polls: 2000 Boolean registers, 125 registers of 16-bit type, or 62 registers of 32-bit type.  The Count includes the number of register values being requested, starting at the Src Data register. 

Dest Data – Enter the starting destination register within this Internal Master's RTDB to place the polled data. Ensure that there is a large enough quantity of registers in the RTDB to store the count. The destination register type should be chosen based on the Source Format of the data.  Booleans should be stored into Boolean RTDB registers. 16-bit values should be stored into 16-bit RTDB registers. 32-bit values or 16-bit pair values should be stored into 32-bit RTDB registers. 
When reading data from internal databases, the Internal Master also reads the quality flag status for each point, and individually sets the quality flags on the destination data to match the source point status. 

Enter the field unit name.

Unit name is displayed in diagnostic menus and in an HCP diagnostic screen. 

Enter the actual field unit address which will be used for the ISaGRAF Field Unit. This Modbus unit address will be referenced under a Slave Channel, from which the ISaGRAF workbench will communicate to the logic program. This should be a unique address from any other Status, Virtual, or Internal Master field unit addresses on the Internal Channel.

Valid addresses 1 to 255. Typically address 1 is used for one ISaGRAF unit (often configured in Channel 15), but if using two ISaGRAF RTUs in the same configuration one of them must be configured for address 123. 

Enter the number of communication retries after a failed poll attempt.

If a poll attempt fails, it will try again up to the configured number of "Com Retries" before the field unit is declared failed. 

Enter the starting holding register to contain the communication status for this field unit.

Each Comm Status takes 5 registers, beginning at the register configured in this parameter. The Comm Status Holdreg for each field unit in a configuration must be defined such that the five registers do not overlap other registers being used.

If the register is defined in the 30,xxx address range, the status values will be stored in the local device's RTDB (i.e., the RTDB defined as a child object to this ISaGRAF Field Unit.

If the register is in the 40,xxx range, the values will be stored in the Status/Control Field Unit RTDB.

The Comm Status Holdreg is optional, and can be set to 0 to disable the storage of status registers.

See the section Communication Status Registers, for a description of the five Comm Status Register contents. 

Select this option to determine whether to produce a Report by Exception (RBE) flag when data in this unit's RTDB changes.

In the RTDB, for every data point, there are potentially 4 RBE flags associated with every data point. When the data point changes, the RBE flags are set. These flags are used to determine when new data needs to be reported to the HCP. 

Click the Edit Table button to define the Modbus polls to be sent to this ISaGRAF field unit. Note that the Poll Table only defines how the Modbus protocol is defined to operate for each set of data defined in the polls. The Poll Table doesn't actually do any of the polling itself. If you want any of these polls to be sent to the ISaGRAF Field Unit on a regular basis, it should be referenced in one or more Scan Table entries in the Internal Channel. 

Source Register – Enter the source register in the ISaGRAF RTU to begin polling data. This will be a Modbus register defined on an I/O board definition in the ISaGRAF logic program. 

Source Format – Enter the data type of the data being requested. See below for a discussion of Source Format options.

See the section   Modbus/Open Modbus TCP Field Unit  for a full discussion on Source Formats. For the ISaGRAF RTU, typically the following Source Formats should be used:

• Boolean – for boards defining Boolean data
• 16 bit register (HL) – for boards defining 16-bit data
• 32 Bit B/B Endian (HLhl) – for ISaGRAF boards defining 32-bit data

Count – Enter the number of registers to poll.
The maximum number allowed in any poll is 2000 Boolean registers, 125 registers of 16-bit type, or 62 registers of 32-bit type.
The Count includes the number of entities being requested, based on the Source Format type listed above.
For instance, if polling 10 sets of 32-bit data which occupy pairs of 16-bit registers (one of the "16 Bit Pair" types of data), the Count should be 10 for the number of entities (not 20 for the number of registers being requested). 

Destination Register – Enter the starting destination register within the RTDB (Real Time Data Base) to place the polled data.
The Destination Register type should be chosen based on the Source Format of the data. 
Booleans should be stored into Boolean RTDB registers.
16-bit values should be stored into 16-bit RTDB registers.
32-bit values or 16-bit pair values should be stored into 32-bit RTDB registers 

Comment - Optional column, allowing a descriptive comment to be entered for each row in the table. The Comment field is unused in the configuration.